Antigen Specific Immunotherapy with Transduced HSC

描述（由申请人提供）：本项目的目的是研究基因修饰的骨髓移植（BMT）诱导有效抗肿瘤免疫的效用。肿瘤免疫治疗的一个主要焦点是开发通过树突状细胞（DC）有效呈递肿瘤抗原来诱导T细胞应答的策略。目前的疫苗接种策略在体内有效负载DC的能力方面受到限制。离体产生的DC可以被有效地负载，但是在再注射后，很少DC运输到次级淋巴器官，其是抗原呈递给T细胞的关键位点。为了提高DC提呈抗原的效率和持久性，我们用编码模型肿瘤抗原的慢病毒载体转导造血干细胞（HSC），然后移植修饰的细胞。我们的研究结果表明，在淋巴器官中的DC的转基因的高水平表达。使用表达抗原的HSC和激活DC的全身性试剂的骨髓移植沿着成熟供体淋巴细胞输注的组合导致抗原特异性T细胞的显著扩增和激活。这种三联疗法为侵袭性小鼠淋巴瘤提供了有效的抗原特异性免疫治疗。在本申请中，我们提出研究对肿瘤的免疫应答的机制和动力学，通过可调节载体选择性表达肿瘤Ag，以及优化治疗策略。具体而言，我们将：（1）以HA作为肿瘤抗原模型，检测小鼠骨髓干/祖细胞（HSCs）经抗原转导后的T细胞免疫应答;（2）研究HSCs转导/移植后体内DC活化和T细胞致敏的分子组合，并开发DC特异性和可调控的载体以增强对抗原的免疫应答;（3）确定骨髓中肿瘤Ag表达对于清髓性和非清髓性同种异体BMT的功效;和（4）确定Ag转导的骨髓的移植是否对实体瘤有效。

DESCRIPTION (provided by applicant): The goal of this project is to investigate the utility of bone marrow transplant (BMT) with gene modified BM to induce potent anti-tumor immunity. A major focus of cancer immunotherapy is to develop strategies to induce T cell responses through efficient presentation of tumor antigens by dendritic cells (DCs). Current vaccination strategies are limited in their ability to efficiently load DCs in vivo. Ex vivo generated DCs can be efficiently loaded, but after re-injection, few DCs traffic to secondary lymphoid organs, which are the critical sites for antigen presentation to T cells. To enhance the efficiency and durability of antigen presentation by DCs, we transduced hematopoietic stem cells (HSC) with a lentiviral vector encoding a model tumor antigen, then transplanted the modified cells. Our results showed high-level expression of a transgene by DCs in lymphoid organs. The combination of bone marrow-transplant using antigen expressing HSC and systemic agents that activate DCs along with mature donor lymphocyte infusions resulted in dramatic expansion and activation of antigen specific T cells. This tripartite therapy provided potent antigen specific immunotherapy of an aggressive established murine lymphoma. In this application, we are proposing to investigate the mechanism and kinetics of the immune response to the tumor, selective expression of the tumor Ag by regulatable vectors, and optimization of the treatment strategy. Specifically, we will: (1) examine the T cell immune responses in mice receiving Ag-transduced bone marrow stem/progenitor cells (HSCs), using HA as a model tumor Ag; (2) investigate combinations of molecules for in vivo activation of DCs and T cell priming subsequent to HSC transduction/transplantation, and develop DC specific and pharmacologically regulatable vectors to enhance immune responsiveness to antigen; (3) determine the efficacy of tumor Ag expression in the BM for myeloablative and nonmyeloablative allogeneic BMT; and (4) determine whether transplantation of Ag transduced BM will be effective against solid tumors.